Karl.... fix Captain Von Trapp's car so that it will start.
~ Zeller ordering Karl to start up the Von Trapps' car due to his suspicions of their attempt to flee.
Karl is a supporting antagonist of the 1959 musical The Sound of Music and its 1965 film adaptation. He is a Nazi lieutenant who serves as the right-hand man of Hans Zeller following the Anschuluss (Austria's annexation into Nazi Germany in 1938).
He was portrayed by Alan Callow.
Following the Anschuluss several days after Captain Georg Von Trapp and Maria Rainer were married, Zeller was appointed as the new Gauleiter of Austria by Adolf Hitler, and Karl is assigned to serve as his new right-hand man. As part of his job, Karl is assigned to help maintain Nazi order around Austria at all costs. During preparations of the Salzburg Music Festival, Karl escorted Zeller as the latter confronts Von Trapp's closest friend Max Detweiller, who is busy preparing Von Trapp's children for the festival while Von Trapp and Maria are on their honeymoon in Paris. Zeller then assured to Max that the Nazi rule over Austria will remain despite the Von Trapps' opposition to it, just he and Karl depart from the stage.
Later on, the delivery boy Rolf Gruber gives the Captain a telegram detailing an offer for him to accept a commission in the Kriegsmarine (the Nazi Navy) at the German Naval base in Bremerhaven (on behalf of Admiral Von Schreiber). Though Von Trapp has no intention in joining the Nazis, Zeller has Karl to gather in several Nazi officers to surround the Von Trapp estate after being alerted by the family's butler Franz, catching the family trying to flee in their car. Von Trapp tried to cover this by claiming that he couldn't get the car to start, but the suspicious Zeller asks Karl to start up the car, which he does instantly without incident. Deducing that the Von Trapp family is trying to flee, Zeller praises Karl for a job well done before confronting Von Trapp with the intent of taking him to Bremerhaven for the commission under Hitler's orders. However, the clever Von Trapp states that he's actually delivering his family for the Festival tonight, with Max presenting out the concert program list to prove the Captain's point. Realizing that it would be much of a little delay, Zeller reluctantly allows this by ordering Karl and the officers to give them an escort to the Festival, stating that he will force the Captain to go to Bremerhaven for the commission afterwards. To ensure of this, Zeller has his several of his men to surround the auditorium on guard duty.
During the festival, Karl watches as the entire audience applauds for the family's singing voices, much to Zeller's annoyance. When Max publicly announces about the commission, the audience seems to be very displeased by this, though Karl smirks at this. The Von Trapp family then concludes their performance with their famous song "So Long" before exiting the stage. During the awards ceremony, Max gave the Von Trapp family enough time to flee from the auditorium by presenting out awards to the runner-ups, just as a Nazi officer informs that the family has fled. Realizing this, an angry Zeller has Karl and his men to patrol the city and track down the Von Trapps. Eventually, their search reaches to an end in a church, where Rolf spots the Von Trapp family before alerting Karl and the others. Fortunately, several of the nuns took the opportunity to sabotage the Nazis' vehicles, allowing the Von Trapps to escape to Switzerland while Zeller, Karl and their men tried in vain to start up their cars.
It is unknown what happened to Karl following the Von Trapps' escape as he wasn't seen or heard from again.
A key difference between the movie and the play:
In the play, the Lieutenant's name wasn't brought up since Rolf addressed him as 'Lieutenant' when locating the Von Trapps.
In the movie, the Lieutenant was given a name (Karl) as he was first addressed by Zeller.